Ecological Risk Characterization in a Military Heavy Metals– and Explosives-Contaminated Site

Potential ecological risks of two heavy metals (Cu, Pb) and three explosives (TNT, RDX, HMX) were determined for a military gunnery range. Since a portion of the site will be submerged after the construction of a flood control reservoir, risk assessment of the site was conducted over two time points: at the current state and after the construction of the flood control reservoir. Terrestrial plants, terrestrial invertebrates, birds, mammals, and aquatic invertebrates were selected as affected ecological receptors at the study site. Potential noncarcinogenic risk was found only in one terrestrial site for Cu and RDX at both time points: For terrestrial plants, ecological hazard quotient (EHQ) by Cu was 1.22. For terrestrial invertebrates, EHQs for Cu and RDX were 1.38 and 6.47, respectively. EHQs in the aquatic environment increased to some extents after the reservoir construction, but the values were less than 1.0. A comparison between EHQs before and after the construction for the same site shows that the reservoir construction would not significantly increase the overall ecological risk, suggesting that the reservoir construction influenced the potential ecological risks at the study site, but the changes were acceptable. Uncertainties involved in the assessment process were identified and discussed.     

Length-Weight Relationship analysis of four freshwater fish Species from Doyang reservoir at Nagaland,India

The LWRs (length–weight relationships) of four freshwater fish species from medium categorized Doyang reservoir at Wokha District, Nagaland were studied, namely as Garra naganensis Hora, 1921; Devario naganensis Chaudhuri, 1912; Chagunius nicholsi Myers, 1924 and Schistura manipurensis Chaudhuri, 1912. Fish sample were collected in every 15 days interval by cast-nets (1.0 × 1.0 cm mesh size covering the 4.5 m² areas), gill-nets (0.4–5.0 cm mesh size), scoop-nets (mesh size with 0.3 × 0.3 cm to 0.6 × 0.6 cm) and also from the local fishermen in between July 2017 to January 2019. The regression value of slope (b) is fallen into 2.860–3.115 range with significant correlation values (r² ≥ .960).     

Zooplankton of a flooded opencast sulphur mine

The zooplankton community of a flooded opencast sulphur mine was investigated during two years. The complicated physical and chemical relationships in this water-filled pit caused an atypical plankton assemblage. At the time of the investigation 20 species of rotifers, 6 of Cladocera, and 8 species of Copepoda were found. A single Ostracod and Chaoborus flavicans were also noted in the samples. Usually the epilimnion was monopolised by rotifers whereas the hypolimnion had a more diversified assemblage of rotifers, cladocerans and copepods. The result of clustering analysis indicated that each predator was associated with its own group of prey. Discrimination analyses showed weak seasonal differences in the zooplankton and three zones in the vertical profile – epilimnetic, upper hypolimnetic and anaerobic. Principal component analysis reduced the chemical parameters to the main contributors of conductivity (the main anions and cations) plus toxic sulphide and hydrogen sulphide. The animals were classified by the first two components into two groups: cold stenotherms and medium-sized filtrators, such as Bosmina longirostris. A specific analysis of vertical profiles generated five variants of diel vertical migrations. When time–space distributions of the plankters were analysed the highest numbers of different species were usually in different times and depths. The epilimnion was inhabited by small fishes and was dominated by rotifers but was free from C. flavicans which inhabited the cold hypolimnion, together with the remaining invertebrate predators (copepods and Asplanchna).Chaoborus and the other invertebrate predators participated more evenly in the contributions of species to the total density. In the presence of invertebrate predators the structure of the rotifer population shifted from soft-bodied species to spined or fast-moving species. When the predation pressure was too strong, as in the hypolimnion, the soft-bodied species were, in practice, absent. When the pit was in an oligotrophic state the hypolimnion population was composed of up to 60–90% rotifers. When the trophic state shifted to mesotrophy, the proportion of cladocerans increased.     

Function of calcium phosphate renal concrements in extant Nautilus: a paradigm for Cambrian-relict short-term mineral reserve equivalent to vertebrate bone

Renal uroliths (concrements) of calcium phosphate have long been known to exist in both growing and mature (non-growing) Nautilus specimens, but to date no evidence-based explanation for their existence has been available. The currently favored speculation is that they function as a calcium reserve for shell and septal calcification. Here we present new observational and experimental data that are consistent with the hypothesis that they serve as a mineral/ion reserve, allowing short-term (<1 day) addition of ionized calcium and phosphorus to blood and other body fluids, in a way analogous to that of vertebrate bone. In both in-ocean experiments and during long-term observation of captive nautiluses, concrements disappear during two different, energy-intensive activities involving removal of anions and cations from newly secreted cameral liquid in the chamber formation cycle, and during dives to depths requiring high osmotic pressures within the canaliculi of the siphuncular epithelium to keep previously emptied chambers from flooding due to suddenly increased ambient hydrostatic pressure. New concrements reappear at other points in the chamber formation cycle and when normal living depth is restored. The use of concrements as an ion reserve and the Cambrian ancestry of nautiloids indicate that Nautilus may exemplify a solution to the problem of energy supply in newly evolved swimmers of the Cambrian radiation independent of that seen in fish.     

Colonization and succession of benthic macroinvertebrates in a new reservoir

The purpose of this study was to examine the colonization and succession of benthic macroinvertebrates in shallow areas (<7 m) of Lake Anna, a new mainstream impoundment in the southeastern U.S.A. Benthic macroinvertebrates were sampled for the first three years after filling by means of artificial substrates placed on the bottom and retrieved with SCUBA. Lake Anna was well colonized by benthic macroinvertebrates during the summer season immediately after impoundment. The total density of organisms increased in each of the first three years. Major changes in the fauna occurred between the first and second years, but the changes between the second and third years were more subtle. The fauna could be divided into two distinct groups based upon the time when the organisms were most consistently abundant. The first colonizers appeared to be dependent upon the components of the former terrestrial ecosystem for food and habitat. As autochthonous factors began to regulate succession, diversity increased and the dominant species shifted to an assemblage of second colonizers. These factors included: (1) decomposition of terrestrial vegetation and detritus leaving bare substrate, (2) sedimentation, (3) improved food quality of the organic matter in the sediment because of ingestion and egestion by the organisms themselves, (4) increased plankton populations, and (5) appearance of macrophytes. As the second colonizers became firmly established in the third year, distinct patterns of spatial distribution began to appear among species with similar niches.     

The temporal distribution pattern of copepods in Corumbá Reservoir,State of Goiás,Brazil

The present study analyzed the pattern of temporal distribution of planktonic copepods in a recently formed reservoir and investigated whether there were differences in the predominance of species. The animals were collected at six stations in the limnetic zone of the central body and lateral arms of the reservoir with a motorized pump at different depths, from December 1996 through November 1998. Three species of Cyclopidae (Thermocyclops decipiens, Thermocyclops minutus and Mesocyclops longisetus) and one species of Diaptomidae (Notodiaptomus iheringi) were recorded. Adults and young, mainly nauplii, of the cyclopoids were predominant during the entire study period. Calanoids became numerically important after the third month following reservoir formation, in some months becoming approximately as abundant as the cyclopoids. There was succession in the abundance of the species, with T. decipiens predominating in the first six months, N. iheringi at the end of the first year, and T. minutus at the beginning of the second year. The differences in water level in the dry and rainy seasons and the operation of the reservoir affected the dynamics of certain copepod species.